Snubbing apparatus for use with a portable drilling mast



J. R. WOOLSLAYER Oct. 25, 1966 3,280,520

SNUBBING APPARATUS FOR USE WITH A PORTABLE DRILLING MAST Filed June 10, 1964 2 Sheets-Sheet l m a RI. m mA V NP 0 J Oct. 25, 1966 J. R. WOOLSLAYER 3,280,520

SNUBBING APPARATUS FOR USE WITH A PORTABLE DRILLING MAST Filed June 10, 1964 2 Sheets-Sheet 2 United States Patent 3,280,520 SNUBBING APPARATUS FOR USE WITH A PORTABLE DRILLING MAST Joseph R. Woolslayer, Tulsa, Okla, assignor to Lee C.

Moore Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed June 10, 1964, Ser. No. 373,998 2 Claims. (61. 52-116) This invention relates to oil well drilling apparatus, and more particularly to means for snubbing an upwardly swinging pivoted mast during erection after it passes its balance point.

When portable drilling masts are swung from a prone position up to an erect drilling position they generally reach their balance point or dead center position before reaching final vertical position. Therefore, after they pass the balance point they swing by :gravity the rest of the way, but to keep them from striking the gin poles too hard it is the practice to snub the fall of such a mast by means of a snub line connected thereto at a high elevation and to the winch of a utility truck. The fall or settling of the mast into final posit-ion therefore can be controlled by the winch operator. When it is decided to take down the mast, the snub line and winch are used to pull the mast forward until it passes through its balance point, and then it can descend by gravity under the control of the drawbacks connected through the line that supports the travelling block to the usual s-lingline.

It is among the objects of this invention to provide a means of snubbing a mast being erected which is automatic, which does not require a winch truck or the like, which is under the control of the draww'orks operator, which can be used for starting a mast down when it is to be swung down from erect position, and with which the extent of the load on a snub line is immaterial.

In accordance with this invention the travelling block in a reclining open-front mast is connected with a track extending lengthwise of the inside of the mast so that the block must always travel along the mast in a set path. A snub line has one end detachably connected to the travelling block, to which a slingline also is connected, while adjustable means connects the opposite end of the snub line to a stationary anchor point apart from the mast in the vicinity of the crown block of the reclining mast. The snub line is of such a length that it will become taut as soon as the mast swings rearwardly past its balance point, whereupon lowering of the travelling block will control swinging of the mast the rest of the way into vertical position. When it is desired to lower the mast, the snub line is shortened so that raising of the travelling block in the upper part of the mast will cause the snub line to swing the mast forward past its balance point, at which point the slingline will become taut and will control the descent of the mast to the ground.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a side view, with parts broken away, of a reclining m-ast equipped with my snub line;

FIG. 2 is a similar view of the mast in erect position; and

FIG. 3 is an enlarged cross section of the mast, taken on the line III-III of FIG. 2.

Referring to the drawings, a mast substructure or base 1 is located at the well site, where it may be mounted on the ground, on a marine platform or on a barge 2 or the like, depending on where the drilling is to be done. Mounted in front and rear shoes 3 and 4 on the base are the upwardly converging legs of a gin pole 5. Pivotally mounted at 7 in the front shoes are the feet of "ice a reclining mast 8 that extends forward away from the base. The front end or head of the mast rests on a suitable ri-gid support 9. Secured to the head of the mast is the usual crown block 11, through which pass lengths of a line 12 that extends back through the mast to a travelling block 13 near the base. Another part of this line extends from the crown block back above the mast and down around a sheave 14, journ-aled midway between the upper ends of the front legs of the gin pole, to drawworks 15 mounted on the base. It will be seen that when the drawworks is operated to wind up the line, the travelling block will be pulled forward toward the crown block.

To aid in erecting the mast, a slingline 17 is used, which is doubled on itself to form a loop over the hook 18 of the travelling block. The sling extends back beneath a pair of laterally spaced sheaves 19 journaled in the mast adjacent its heel, and on out behind the mast to the gin pole, to which it is connected at the upper ends of the front gin pole legs. When the dr-awworks is operated to pull the travelling block toward the crown block, the sling is pulled in the same direction farther into the mast, so the sling helps in a well-known manner to swing the mast upward and backward toward upright position against the gin pole.

It is a feature of this invention that as soon as the rising mast passes through its center of gravity or balance point represented by the broken line B in FIG. 2, movement of the mast from that point under the influence of gravity to final upright position is snubbed automatically so that the mast will not crash against the gin pole. Accordingly, a snub line 21 is provided that is detachably connected at one end to the travelling block hook in the reclining mast, and anchored at its opposite end to support 9 or some other support in the vicinity. Also, the travelling block is suspended from a track that extends lengthwise of the mast. As shown best in FIG. 3, such a track can be formed from a pair of parallel channels 22 attached to the inside of the mast adjacent its back for supporting a pair of wheels 23 that carry a yoke 24 attached to the hook. The snub line is of such a length that it will not be pulled taut by the travelling block until just after the mast passes over dead center and starts to swing by gravity toward vertical position. The initial taut position is represented by the left-hand dotted position of the travelling block in FIG. 2. At that time the tightening of the snub line will stop the mast until the travelling block is allowed to descend, whereupon the sling will become slack and the snub line will permit the mast to settle back toward the gin pole at a controlled rate determined by the slowly descending travelling block, which is under the control of the drawworks operator. The track prevents the snub line from pulling the hook forward out of the mast. A guard 20 at each sheave 19 prevents the slack sling from becoming completely disengaged from the sheaves. After the mast has engaged the gin pole, they can be fastened together in a well-known manner and then the travelling block can be quickly lowered so that the sling and snub line can be disconnected from it.

Another feature of this invention is that the snub line also can be used for pulling the erect mast forward past its balance point when the mast is to be lowered. For this purpose a shorter snub line is used, which preferably is produced by shortening snub line 21. This can be done by any suitable means, such as by a turnbuckle 26 connecting the lower end of the snub 'line with support 9. The amount of shortening has to be predetermined. With the travelling block in its lower position, the sling and snub line are attached to the hook and then the hook is raised until the snub line becomes taut at the dotted line position of the 'hook in the erect rn-ast. This position of the hook necessarily will be lower in the mast than when the snub line was longer at erection time, and it will be such that as the travelling block is pulled up in the mast the snub line will swing the mast forward to a point just in front of its center of gravity (the righthand dotted position of the travelling blockin FIG. 2) before the slin-g becomes taut and prevents the mast ctrom falling forward. Lowering of the mast. from there to reclining position then is under the control of the travelling block and sling as is customary.

It will be seen that by using the snubbin'g apparatus diclosed herein the mast is snubbed automatically as soon as it rises past its balance point, and that after the snub line has been shortened the erect mast can be pulled forward past its balance point by merely raising the travelling block. There is no need for a wine-h truck or the like, so the invention is especially useful where such a truck could not be used, such as on a barge. The need for a winch operator likewise is eliminated, because snubbing and lowering of the mast is under the control of the drawworks operator.

According to the provisions of the patent statutes, I

have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim: i

1. Snub bing apparatus for use with a mast base having front and rear ends, a reclining mast extending ttorward away from the base and having front feet hinged to the base, the reclining mast having an open lower side, a crown block mounted on the head of the reclining mast, a fixed member adjacent the crown block and independent of the mast, a travelling block inside the mast near said base, drawworks on the base, a line connecting the travelling block with the crown block and the drawworks, a slingline detachably connected to the travelling block and extending rearwardly out of the mast, and means on the base behind the mast connected with the slingline so that when the drawworks is operated to pull the travelling block toward the crown block the mast will be swung up past its balance point toward upright position; said apparatus comprising a track inside the mast extending lengthwise thereof, means connecting the travelling block with the track, a snub line having one end detachably connected to the travelling block, stationary anchor means connected to said fixed member, and means connecting the opposite end of the snub line to said anchor means, the snub line being short enough to become tau-t as soon as the mast swings rearwardly past its balance point so that lowering of the travelling block in the mast then will control swinging of the mast the rest of the way to upright position.

2. Snubbing apparatus according to claim 1, in which said connecting means is adjustable so that before the upright mast is lowered the snub line can be shortened so that subsequent raising of the travelling block in the upper part of the mast will cause the snub 'line to swing the mast forward past said balance point.

References Cited by the Examiner UNITED STATES PATENTS 2,787,344 4/ 1957 Woolslayer et a1 52120 2,963,124 12/1960 Woolslayer et al. 52-210 X FRANK L. ABBOTT, Primary Examiner.

R. S. VERMUT, Assistant Examiner. 

1. SNUBBING APPARATUS FOR USE WITH A MAST BASE HAVING FRONT AND REAR ENDS, A RECLINING MAST EXTENDING FORWARD AWAY FROM THE BASE AND HAVING FRONT FEET HINGED TO THE BASE, THE RECLINING MAST HAVING AN OPEN LOWER SIDE, A CROWN BLOCK MOUNTED ON THE HEAD OF THE RECLINING MAST, A FIXED MEMBER ADJACENT THE CROWN BLOCK AND INDEPENDENT OF THE MAST, A TRAVELLING BLOCK INSIDE THE MAST NEAR SAID BASE, DRAWWORKS ON THE BASE, A LINE CONNECTING THE TRAVELLING BLOCK WITH THE CROWN BLOCK AND THE DRAWWORKS, A SLINGLINE DETACHABLY CONNECTED TO THE TRAVELLING BLOCK AND EXTENDING REARWARDLY OUT OF THE MAST, AND MEANS ON THE BASE BEHIND THE MAST CONNECTED WITH THE SLINGLINE SO THAT WHEN THE DRAWWORKS IS OPERATED TO PULL THE TRAVELLING BLOCK TOWARD THE CROWN BLOCK THE MAST WILL BE SWUNG UP PAST ITS BALANCE POINT TOWARD UPRIGHT POSITION; SAID APPARATUS COMPRISING A TRACK INSIDE THE MAST EXTENDING LENGTHWISE THEREOF, MEANS CONNECTING THE TRAVELLING BLOCK WITH THE TRACK, A SNUB LINE HAVING ONE AND DETACHABLY CONNECTED TO THE TRAVELLING BLOCK, STATIONARY ANCHOR MEANS CONNECTED TO SAID FIXED MEMBER, AND MEANS CONNECTING THE OPPOSITE END OF THE SNUB LINE TO SAID ANCHOR MEANS, THE SNUB LINE BEING SHORT ENOUGH TO BECOME TAUT AS SOON AS THE MAST SWINGS REARWARDLY PAST ITS BALANCE POINT SO THAT LOWERING OF THE TRAVELLING BLOCK IN THE MAST THEN WILL CONTROL SWINGING OF THE MAST THE REST OF THE WAY TO UPRIGHT POSITION. 